In multiple port switching networks, ports are usually linked together in pairs in what can generically be referred to as a transmit/receive arrangement. In such a connection, one of the ports serves as a source of for example, voice/data information while the other port serves as a destination in a communication process. These roles can be exchanged during the communication process.
There exists a class of communication requirements where the connectivity is much more demanding than simple port pairing in that groups of more than two ports must be linked together in a conference. In a conference, three or more ports are involved in the communication process. Any given port may at various times transmit to all other ports in the conference. There have been a variety of techniques developed to deal with the greater demands of the connectivity of a conference. Phiet U.S. Pat. No. 4,644,530 discloses an instant speaker algorithm for a digital conference bridge. The digital conference bridge is for use with a plurality of telephones and arranged whereby, the output signal from one telephone is directed to the remainder of the telephones and the output signals of the remainder are suppressed.
U.S. Pat. No. 4,577,065 discloses a meet-me conference arrangement. The meet-me conference arrangement is for use in a telephone switching office. An access code is assigned to each conference and at an agreed upon time, all conferees for a conference dial the same access code. The switching office allocates a bridging system in response to the first call to arrive at the office.
Barangai et al U.S. Pat. No. 4,575,845 discloses a time division multiplex conference. The time division multiplex conference continuously sums and outputs digital message samples received from N subscribers in N respective time slots. Message samples collected from each subscriber of a conference connection are summed during a first time frame and outputted during a second time frame.
Reed U.S. Pat. No. 4,339,816 discloses a conferencing apparatus and methods for a frequency division multiplex communications system. The conferencing apparatus employs a first available band sideband for communication and a second sideband for signaling. Each subscriber in the system has dual receiving and transmitting equipment which enables a subscriber to communicate with any other subscriber.
Herr et al U.S. Pat. No. 4,544,804 discloses a conference control transfer arrangement. The conference arrangement has certain speaker priorities and control capabilities provided to the originator. The originator under the guidance of voice prompts, can transfer this control to another party on the conference.
The problem that exists in current conferencing apparatus is the limitation to the number of parties to the conference due to the increase in noise and breakdown of signal level control. The present invention is a conferencing module which is capable of providing, among other features, the necessary combining of information signals together with appropriate signal level controls and filtering to satisfy conference requirements. The invention can be used as a building block module for the design of conference arrays or they can be inserted into multistage switching networks not explicitly designed for conferencing to raise their functionality to a more general capacity.